I don't understand why Google wants me to have this omnipresent search bar on every home screen if there obviously is Google Now / Google Search embedded into the launcher if you go to the left page. So after some searching I found a way to hide it. But it will show again if you go to the left screen; no functionality is lost. Of course digging through the code I found some more things which are customizable :)

System UI:
- hide clock on default homescreen
- open the app drawer when pressing the home button on default homescreen
- change the icon of the home button to an app drawer icon on default homescreen
- go to sleep when pressing back button on every screen or only on default homescreen
- change the icon of the back button to a power off button